Research On The Influence And Control Measures Of The Adjacent Subway Tunnel Of The Deep Excavation In Haidian Park

With the rapid development of modern economy and science and technology,urban environmental conditions are becoming more and more complex.With the continuous expansion of the scale and depth of excavation,the influence of the unloading,dewatering and vibration caused by the excavation will inevitably change the displacement field and stress field around the excavation.Eventually,the adjacent tunnel will be adversely affected even damaged.So based on the importance of tunnel and the sensitivity of its structure,it has wider significance to scientifically predict and infer the impact of excavation on the tunnel and its structure,as well as reduce the impact through reasonable and effective measures.Based on Haidian Park’s deep excavation,this article analyzed the influence of deep excavation on the deformation of adjacent tunnel and the defensive measures by the theoretical calculation and numerical simulation,at last compared the reinforcement effects of different measures.The following are the main achievements:(1)Through theoretical calculation method,calculate the additional load of adjacent tunnel by the use of Mindlin solution,analyzed the effective stress variation of tunnel outside the deep excavation caused by dewatering,used Pasternak foundation model to establish the differential equation of tunnel displacement,finally calculate and analysis the vertical and horizontal deformation of tunnel by the use of MATLAB.Then found the change of tunnel effective stress is caused by pit water level and seepage,tunnel’s deformation changes large within the scope of the excavation,and the farther the distance from the tunnel,the tunnel deformation is smaller.The vertical displacement of the tunnel is mainly produced by the bottom unloading stress,the horizontal displacement is mainly composed of adjacent side of foundation pit lateral wall of the unloading stress,the rest of the side displacement influence the tunnel little.(2)In order to study the deformation law of supporting structure of adjacent subway tunnel near Haidian Park under dewatering and excavation conditions,mechanism Fl AC3 D software is used to conduct numerical simulation calculation,and fluid-structure coupling method is adopted to simulate the dewatering process.Firstly,the analysis shows that the dewatering will cause settlement of the tunnel.Secondly,if the tunnel is far or close the excavation,the vertical uplift of the tunnel is large or little.Finally,the closer the horizontal distance between the tunnel and the excavation,the larger vertical tensile deformation is of the tunnel,because the tunnel center line is close to the bottom of the excavation,the horizontal tensile ratio of the tunnel has no obvious difference.(3)The influence of different prevention and control measures on the project was analyzed through numerical simulation,and the effects of control measures such as reinforce the diaphragm wall,internal support,isolation pile reinforcement,soil outside the excavation,tunnel structure were analyzed,and the comprehensive control measures and parameter selection suitable for the project were given,at last give the control measures and parameter selection which are suitable for the project.It is find that continuous wall reinforcement effect poor,internal support and isolation piles respectively well on the horizontal and vertical displacement,soil strengthening and tunnel grouting has good control effect of both displacement.The tunnel displacement is effectively controlled by the reinforcement measures of internal support,isolation pile and tunnel,which meets the standard of the code and has a certain fault tolerance.